I'm not a big advocate for antivirus software, only because it starts fights. But, if I do suggest anything, it would be Kaspersky PURE Total Security. However, this is over $70 I believe. But, if you haven't already gotten your Facebook free subscription to security software: https://www.facebook.com/security/app_360406100715618 then go for it!

In the AV Marketplace at Facebook, they offer Kaspersky PURE Total Security for free among others.